Clear ^6 for Mason Stains

Someone may have tested the formula recommended by Mason and could supply some input. I could not get an email response from them so I called on the phone. They recommend the following transparent large cone 6 for most of their colors.

F-38 frit 32%

Kona F-4 Spar 26%

Silica 19%

Whiting 13%

EPK 10%

The formula looks quite old. F-38 is and odd frit by Fusion Co. that contains about 18% strontium carbonate. The closest Ferro frit is 3292, but it only has 4% strontium and other components of 3292 are not close. I personally don't think that amount of strontium is going to influence the colors very much.

For the other components of F-38 the Ferro frit 3124 is fairly close, but it does not contain strontium. When I get around to testing this formula, and to avoid finding F-38, I will use 3124 and test with and without about 10% added strontium carbonate to see if it indeed affects the colors significantly.

it doesn't matter much which clear you use as long as you avoid glazes with tin in them. if you need it more opaque ... throw some zircopax in it .... but it generally makes your glaze look like plastic.

Thank you everyone for taking the time to reply.
Looks like at least two formulas are using 3124 which should be a good flux for the clear base.
I'm familiar with the "plastic" look and don't like it.
Great comments, thanks.
John255

Atomic Axe,
You mention the "Plastic Look", but also I find most ^6 electric formulas for transparent glazes to be far too glossy.
The clear formulas in reduction I'm accustomed to seem more toward satin, but still quite transparent.
Here is a formula that fits the too glossy and plastic look, but very good in all other aspects.

Silica -20
EPK -20
G-200 Spar-20
Wollastonite-15
3134-25

What do you think about this?
John255

(BTW, I've been following your post and find your comments to be right on.
However, I think you are shooting yourself in the foot with that avatar photo?)

Mason stains have several requirements that need to be followed to get the most accurate color development. See the reference chart HERE. Some need zinc, some don't, some need a specific amount of calcium, others don't, some go so hot, others don't. There's a lot of variation in how they behave. So start with that, and adjust your glaze as needed to work with whatever stain you're using.

Hmm, should be fine I guess, will be a little more stable and the wollastonite is just whiting with silica in almost equal parts so really it's about 7.5 whiting and 27.5 flint.

if it turns out to not be fluid enough, you can easily tweak it by adjusting the flint and kaolin down slightly to increase the frit. especially since there is so much silica in the glaze that will raise the melting temp.

And by plastic, I mean plastic, not glossy. Glossiness can be made soft buttery matte with dolomite ... zircopax makes glazes look like cheap formed plastic in high quantities. So, i normally keep it in 5% max quantities since all you are looking for is to make it opaque, not absolutely white for a base. If you were going for just oxide use, I would suggest tin since you can get it to break and it does some fun stuff with oxides (raspberry red is chrome and tin in a glaze) ... but with the cost and ability to change colorants like certain stains (reds in particular) a tiny amount of zircopax will let you do things like be able to layer more subtle colors like blues, greens and reds over harsh colors like blacks, dark blues and browns without watching them just fade away.

This glaze has both zircopax and dolomite. The small dose of dolomite makes the glaze that soft buttery matte. With the higher melt and the higher amount of zircopax do you see how the glaze doesn't break on edges even if it does move and it looks more like melted plastic on top of the clay? that is the zircopax at play.

but ... with that glaze there, take the cobalt ox out and you can easily have so soft buttery white base to add mason stains to, though I would probably flip the percentages of feldspar and gerstley ... But I like my glazes with a little more movement.

Attached Files

Mason stains have several requirements that need to be followed to get the most accurate color development. See the reference chart HERE. Some need zinc, some don't, some need a specific amount of calcium, others don't, some go so hot, others don't. There's a lot of variation in how they behave. So start with that, and adjust your glaze as needed to work with whatever stain you're using.

I respectfully disagree with your assessment of zircopax. I really don't have a problem with it. I think it all depends on the base glaze. I find I need to use at least 8% to get true opacity, and all of my glazes still break just fine. I think it depends on the fluidity of the glaze as to whether or not it will break, not the zircopax. I have several glazes with 8-10% and we always use them on textured pieces and they break very well. I agree that tin tends to do nicer things with the color, warms them up a bit, but the way prices rocketed up recently I am happy to switch to zircopax.

Oh, don't get me wrong ... I love zircopax ... it's my go to opacifier and i have no problem with going up to 10%, I will try to make it work with 5% max though ... i've just experimented with it to the point that I know that it gets plastic looking if not tweaked right. But with the cost of tin almost making you have to offer your first born for it in cost ... I will always love zircopax.

This is a good discussion with valuable comments added by all.
I think I did not make it very clear that the base glaze for Mason stain additions up to 10% was meant to transparent.
My compliant is that most formulas for transparent and semi-transparent are very glossy to the point of distraction.
In reduction the effect is different.
The comment about Wollastonite having so much silica could be a glossy factor because apparently there is enough flux to produce a good melt.
And, yes I too like a glaze that moves a bit to bring life to the piece.
Thanks for your thoughts.
John255